Harold Widner clears a fallen tree from his truck in Arlington, Texas on Tuesday, April 3, 2012. Several reported tornadoes tore through the Dallas area on Tuesday, tossing semis in the air and leaving crumpled tractor trailers strewn along highways and in truck stop parking lots. The National Weather Service reported at least two separate "large and extremely dangerous" tornadoes south of Dallas and Fort Worth.

Flying debris greatest danger when tornado strikes

The severe thunderstorm season runs from April through June across the South Plains, and violent storms most often occur in the 30 days from about mid-May to mid-June, according to the National Weather Service.

The severe thunderstorm season runs from April through June across the South Plains, and violent storms most often occur in the 30 days from about mid-May to mid-June, according to the National Weather Service.

“We recommend that people have at least two or three ways to monitor severe weather conditions,” said Jody James, warning coordination meteorologist at the NWS.

“Those can be radio/TV, Internet and NOAA Weather Radio. And there are a lot of good apps out there for Droid phone and iPhone,” James said.

“Ideally, you should have more than one way so you can have some redundant means to monitor the weather information.”

For individuals who have no basement or hardened, above-ground shelter, interior rooms and small rooms such as closets or bathrooms offer some possibility of protection in a tornado, said Ernst Kiesling, professor of civil engineering at Texas Tech and executive director of the National Storm Shelter Association.

“My best advice would be to seek a place of refuge in the central part of the building at the lowest level,” he said.

“There’s an advantage in the small room such as a hallway, closet or bathroom — put as many walls between you and the outside as possible.”

James said, “A tornado sort of works from the top down and the outside in. So, if you can put more than one wall between you and the outside, you are increasing your chances of surviving considerably.

“You still want to wrap up in a blanket or mattress because flying debris is the main culprit.”

Measures offering the best protection include a concept Kiesling worked on following the May 11, 1970, tornado in Lubbock.

That storm, classified as being among the most violent of tornadoes, struck the downtown area, killing 26 people and causing an estimated $500 million in damage. It destroyed a number of homes in surrounding residential areas, along with the Cumberland Presbyterian Church, and heavily damaged commercial buildings.

President Richard Nixon designated Lubbock a disaster area.

The fruition of Kiesling’s research led to the construction of inside, above-ground “safe room” shelters that can withstand most tornadoes.

“In about 1972, the concept of the above-ground storm shelter emerged because when we looked at some of the damaged houses, it became evident that a portion of the house was still standing. Oftentimes it was a closet or bathroom or something in the interior part of the house that was still standing. So, we reckoned that if we put a little effort into hardening and stiffening that small room, then we could economically provide a very high degree of occupant protection at minimum cost.”

Kiesling said, “FEMA published in 1998 the booklet called ‘FEMA 320: Building a Safe Room Inside your House.’ That included most of the designs we have developed. That has remained very much the same, and it’s a booklet that has several prescriptive designs for hardening and stiffening a small room inside the house.”

Kiesling said the greatest number of possibilities for a safe shelter are offered in the construction of a new house.

Although it’s labor intensive, a safe room also can be constructed inside an existing home.

“One can retrofit and harden and stiffen an existing room,” Kiesling said. “But you pretty well have to strip the sheeting, the sheetrock and so forth, and get to it from one side or the other. So, it’s kind of a mess to retrofit in an existing house.”

The National Storm Shelter Association, which has written standards to keep up the integrity of storm shelters, recognizes those who comply by allowing them to become producer members. Information is available on its website: www.nssa.cc.

James said conditions that accompany tornadoes include the three ingredients that make any kind of thunderstorm: moisture, lift and instability.

“We have a fourth ingredient that differentiates what would be a single-cell thunderstorm — a garden-variety type that you might see down on the Gulf Coast in the summertime versus the storms we see out here in the spring — and that’s wind shear.”

He added, “Wind shear is just a situation where the winds are turning and usually increasing as you go up like a corkscrew. And basically what happens in these strong thunderstorms, we convert some of the corkscrew-turning winds into a thunderstorm updraft so the whole updraft begins to rotate.

“And when we do that, we set in motion a whole series of events that lead to large hail, downburst winds, heavy rain and tornadoes.

“We call those supercell thunderstorms.”

To comment on this story:

ray.westbrook@lubbockonline.com • 766-8711

leesha.faulkner@lubbockonline.com • 766-8706

Increasing safety

■ Good shelters: Hardened, above-ground shelters.

■ Without safe rooms: Move to the center of the building, and to the lowest level.

■ Relative safety: Find a small closet or bathroom.

■ Walls: Put as many interior walls between you and the outside as possible.

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